Hybrid solid electrolyte with the combination of Li7La3Zr2O12 ceramic and ionic liquid for high voltage pseudo-solid-state Li-ion batteries

Abstract

Concerning the safety aspects of high-voltage Li-ion batteries, a pelletized hybrid solid electrolyte (HSE) was prepared by blending Li₇La₃Zr₂O₁₂ (LLZO) ceramic particles and an ionic liquid electrolyte (ILE) for use in pseudo-solid-state Li-ion batteries. The LLZO particles are enclosed by the ionic liquid as a LLZO–ILE matrix, and are quantified by FESEM elemental mapping. The chemical stability of the LLZO in the ILE is confirmed by powder XRD and FT-IR analysis. The HSE, with an optimized weight ratio of 80% LLZO, 19% Py₁₄TFSI, and 1% lithium bis(trifluoromethanesulfonyl)imide, exhibits good thermal stability, even at 400 °C. The optimized HSE reveals an ionic conductivity of 0.4 × 10⁻³ S cm⁻¹ and an electrochemical stability of 5.5 V with Li metal. Pseudo-solid-state Li-ion cells are fabricated using the HSE, and afford initial charge–discharge capacities of 140/130 mA h g⁻¹ (Li/HSE/LiCoO₂) with 99% capacity retention at the 150^th cycle. The scope of the HSE is widened to high-voltage (>8 V) pseudo-solid-state Li-ion batteries through a bipolar stacked cell design. Dendrite formation is hindered during cycling in the Li-ion cell. Hence, the present investigation will greatly contribute to the next generation of high-voltage pseudo-solid-state Li-ion batteries.